TY - JOUR

T1 - The parameter dependence of eddy heat flux in a homogeneous quasigeostrophic two-layer model on a b plane with quadratic friction

AU - Chang, Chiung Yin

AU - Held, Isaac M.

N1 - Funding Information:
Acknowledgments. We thank Junyi Chai for sharing the doubly periodic quasigeostrophic model code with us and Tsung-Lin Hsieh for the help of model setup on GFDL RDHPCS. An earlier version of this work is presented in CYC’s doctoral dissertation, which was kindly read by Pablo Zurita-Gotor, Steve Garner, and Bob Hallberg. Suggestions on the presentation by the three anonymous reviewers have been incorporated into the final version. CYC’s graduate study was supported by NSF Grant AGS-1733818.

PY - 2021/1

Y1 - 2021/1

N2 - This study investigates the parameter dependence of eddy heat flux in a homogeneous quasigeostrophic two-layer model on a b plane with imposed environmental vertical wind shear and quadratic frictional drag. We examine the extent to which the results can be explained by a recently proposed diffusivity theory for passive tracers in two-dimensional turbulence. To account for the differences between two-layer and two-dimensional models, we modify the two-dimensional theory according to our two-layer f-plane analyses reported in an earlier study. Specifically, we replace the classic Kolmogorovian spectral slope, 25/3, assumed to predict eddy kinetic energy spectrum in the former with a larger slope, 27/3, suggested by a heuristic argument and fit to the model results in the latter. It is found that the modified theory provides a reasonable estimate within the regime where both b~ 5 bk2d2U21 and the strength of the frictional drag, c~D 5 cDk2d1, are much smaller than unity (here, cD is the nondimensional drag coefficient divided by the depth of the layer, kd is the wavenumber of deformation radius, and U is the imposed background vertical wind shear). For values of b~ and c~D that are closer to one, the theory works only if the full spectrum shape of the eddy kinetic energy is given. Despite the qualitative, fitting nature of this approach and its failure to explain the full parameter range, we believe its documentation here remains useful as a reference for the future attempt in pursuing a better theory.

AB - This study investigates the parameter dependence of eddy heat flux in a homogeneous quasigeostrophic two-layer model on a b plane with imposed environmental vertical wind shear and quadratic frictional drag. We examine the extent to which the results can be explained by a recently proposed diffusivity theory for passive tracers in two-dimensional turbulence. To account for the differences between two-layer and two-dimensional models, we modify the two-dimensional theory according to our two-layer f-plane analyses reported in an earlier study. Specifically, we replace the classic Kolmogorovian spectral slope, 25/3, assumed to predict eddy kinetic energy spectrum in the former with a larger slope, 27/3, suggested by a heuristic argument and fit to the model results in the latter. It is found that the modified theory provides a reasonable estimate within the regime where both b~ 5 bk2d2U21 and the strength of the frictional drag, c~D 5 cDk2d1, are much smaller than unity (here, cD is the nondimensional drag coefficient divided by the depth of the layer, kd is the wavenumber of deformation radius, and U is the imposed background vertical wind shear). For values of b~ and c~D that are closer to one, the theory works only if the full spectrum shape of the eddy kinetic energy is given. Despite the qualitative, fitting nature of this approach and its failure to explain the full parameter range, we believe its documentation here remains useful as a reference for the future attempt in pursuing a better theory.

KW - Eddies

KW - Fluxes

KW - Quasigeostrophic models

KW - Turbulence

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U2 - 10.1175/JAS-D-20-0145.1

DO - 10.1175/JAS-D-20-0145.1

M3 - Article

AN - SCOPUS:85098497493

SN - 0022-4928

VL - 78

SP - 97

EP - 106

JO - Journals of the Atmospheric Sciences

JF - Journals of the Atmospheric Sciences

IS - 1

ER -